class Circle {
  constructor(x, y) {
    this.x = x;
    this.y = y;
    this.r = Math.random() * 10;
    this._mx = Math.random();
    this._my = Math.random();

  }

  //canvas 画圆和画直线
  //画圆就是正常的用canvas画一个圆
  //画直线是两个圆连线，为了避免直线过多，给圆圈距离设置了一个值，距离很远的圆圈，就不做连线处理
  drawCircle(ctx) {
    ctx.beginPath();
    //arc() 方法使用一个中心点和半径，为一个画布的当前子路径添加一条弧。
    ctx.arc(this.x, this.y, this.r, 0, 360)
    ctx.closePath();
    ctx.fillStyle = 'rgba(204, 204, 204, 0.3)';
    ctx.fill();
  }

  drawLine(ctx, _circle) {
    let dx = this.x - _circle.x;
    let dy = this.y - _circle.y;
    let d = Math.sqrt(dx * dx + dy * dy)
    if (d < 150) {
      ctx.beginPath();
      //开始一条路径，移动到位置 this.x,this.y。创建到达位置 _circle.x,_circle.y 的一条线：
      ctx.moveTo(this.x, this.y); //起始点
      ctx.lineTo(_circle.x, _circle.y); //终点
      ctx.closePath();
      ctx.strokeStyle = 'rgba(204, 204, 204, 0.3)';
      ctx.stroke();
    }
  }

  // 圆圈移动
  // 圆圈移动的距离必须在屏幕范围内
  move(w, h) {
    this._mx = (this.x < w && this.x > 0) ? this._mx : (-this._mx);
    this._my = (this.y < h && this.y > 0) ? this._my : (-this._my);
    this.x += this._mx / 2;
    this.y += this._my / 2;
  }
}
//鼠标点画圆闪烁变动
class currentCirle extends Circle {
  constructor(x, y) {
    super(x, y)
  }

  drawCircle(ctx) {
    ctx.beginPath();
    //注释内容为鼠标焦点的地方圆圈半径变化
    //this.r = (this.r < 14 && this.r > 1) ? this.r + (Math.random() * 2 - 1) : 2;
    this.r = 8;
    ctx.arc(this.x, this.y, this.r, 0, 360);
    ctx.closePath();
    //ctx.fillStyle = 'rgba(0,0,0,' + (parseInt(Math.random() * 100) / 100) + ')'
    ctx.fillStyle = 'rgba(255, 77, 54, 0.6)'
    ctx.fill();

  }
}
window.requestAnimationFrame = window.requestAnimationFrame || window.mozRequestAnimationFrame || window.webkitRequestAnimationFrame || window.msRequestAnimationFrame;

let canvas = document.getElementById('canvas');
let ctx = canvas.getContext('2d');
let w = canvas.width = canvas.offsetWidth;
let h = canvas.height = canvas.offsetHeight;
let circles = [];
let current_circle = new currentCirle(0, 0)

let draw = function() {
  ctx.clearRect(0, 0, w, h);
  for (let i = 0; i < circles.length; i++) {
    circles[i].move(w, h);
    circles[i].drawCircle(ctx);
    for (j = i + 1; j < circles.length; j++) {
      circles[i].drawLine(ctx, circles[j])
    }
  }
  if (current_circle.x) {
    current_circle.drawCircle(ctx);
    for (var k = 1; k < circles.length; k++) {
      current_circle.drawLine(ctx, circles[k])
    }
  }
  requestAnimationFrame(draw)
}

let init = function(num) {
  for (var i = 0; i < num; i++) {
    circles.push(new Circle(Math.random() * w, Math.random() * h));
  }
  draw();
}

let initSize = 60;
if (navigator.userAgent.match(/(iPhone|iPod|Android|ios)/i)) {
  initSize = 20;
}
window.addEventListener('load', init(initSize));
window.onmousemove = function(e) {
  e = e || window.event;
  current_circle.x = e.clientX;
  current_circle.y = e.clientY;
}
window.onmouseout = function() {
  current_circle.x = null;
  current_circle.y = null;

};

window.onresize = function() {
  // let w = canvas.width = canvas.offsetWidth;
 // let h = canvas.height = canvas.offsetHeight;
 // let circles = [];
 // let current_circle = new currentCirle(0, 0)
 // init(initSize)

}
